It has been proposed to use programmable resistive elements in memory cells to provide non-volatile data storage. Such resistive elements are programmable to adopt one of a plurality of different resistive states. The programmed resistive state is maintained even when a supply voltage of the memory cell is disconnected, and therefore data can be stored by such elements in a non-volatile fashion.
Various types of resistive elements have been proposed, some of which are capable of being programmed by the direction of a current that is passed through the resistive elements. An example of such a current-programmable resistive element is an STT (spin transfer torque) element, which is based on magnetic tunnelling junctions (MTJs).
Due at least in part to the transistors used for programming the resistor states, memory cells based on programmable resistive elements tend to be less compact than other types of memory cells such as those of a RAM (random access memory). There is a general need in the art for a memory cell based on programmable resistive elements having a reduced surface area.